Mold for high temperature castings



Patented Nov. 1, 1932 UNITED STATES PA ENT oFFics LE sun 1 BENSING, orLEBANoN, PENNSYLVANIA, AssIQN mg LEQANQN 5W FOUNDRY, or LEBANON,PENNSYLVANIA, A CORPORATION qsgmmsxw MOLD son men TEMPERATURE q sriNqsN0 Drawing.

This invention relates to a molding sand for foundry purposes that willform molds into which molten metals or their alloys can be poured toform successfully shapes WhlCh '5' have been very difiicult orimpossible to form satisfactorily heretofore in commercial practice. Bythis invention molds are formed into which steel, for example, can becast even though sections of the forms or shapes desired are thin inplaces, or small amounts of the molding sand used are surrounded bylarge amounts of the poured metal.

While this invention has been found to be particularly useful in castinghigh melting point metals such as steel, it is not restricted to thismaterial, since it is also applicable to other metals and alloys forwhich molds have been made of ordinary sand, that is,

silica sand.

Heretofore silica sand has been used both for making .molds proper, aswell as cores for such molds. Different varieties of sand are used forthese purposes, such as river, bank and sea sands, these sands usuallybeing obtained in the vicinity of the place where the foundry is locatedto save freight charges.

Such sands contain various amounts of clay,

which may be fusible at the pouring temeratures of the metals that arebeing cast mto forms. This is satisfactory for metals and alloys whichare cast at relatively low temperatures, but with metals and alloyswhich are cast at very high temperatures, as for example, carbon steelcastings and alloy steel castings, the clays occurring in such sandsflux too readily and burning in of the sand is caused to take place,making the castings unsatisfactory. If the sand has little or no claymixed therewith bonding materials such as wheat flour, dextrine,bentonite, et cetera are mixed with the sand to 've suificientplasticity and strength to it or holding the shapes.

In carrylng out the present invention, zircon,- which is zirconiumsilicate that is found in the natural state in many places of the earthssurface, is used for making the molds or is used for lining molds thatmay be made of ordinary sand or a mixture of ordi-' 60 nary sand andzircon. Zircon is very hard Application flied October 4, 1930. SerialNo. 48( !,5 2(

' and has a much higherfusion. ointthan silica. It does not become powered-byusing it as a molding sand and it has a higher specific gravitythan silica sand, thusiadaptmg it betterfor heavy castings. :The gramsof zircon are usually round and 1 polished, being ordinarily obtainedfrom alluvial deposits, so that the ca'stings that arepoured into moldsmade of, or lined with, zircon, are smooth and .are notinjured.by.burning in-the same. The following are given astwo examplesof mixtures that can be used for making molds containing zircon, but itis to be understood that the invention is. not restricted to theseexamples. I may, for example, use 3% of water, 2% of bentonite and" 95%of ZlI'COll sand, or I may use 1% of water 1% of wheat flour, /47 ofdextrine 97%% of zircon sand.

Zircon that is found in natural deposits is suitable for use in myinvention, although it may contain only about 95% of zirconium silicatewith a small amount of silica sand and organic impurities. Theimpurities may be removed, however, in large part or entirely, stillleaving a very excellent and satisfactory sand for foundry purposes.

By using zircon as themolding sand the danger of burning in occurring ispractically eliminated and less scabbing of the castings takes place;the castings can be molded to closer dimensions, thus reducing machiningcosts; the metal may be poured in hotter than with silica sand and thegates that are used with silica sand may be eliminated and the castingspoured down through risers. Also it is possible to pour heaviercastings, as the metal penetrates the high specific gravity zircon lessthan it penetrates ordinary sand molds. The zircon sand is suitable foruse not only as the molding sand, but also for making cores for molds,the usual binders, such as oil, farinaceous materials, rosin, et ceterabeing used. For example, by using zircon cores only three eighths of aninch square may be removed easily in cast steel blocks that are sixinches square at the base and 12 inches high, as the core does not formwith the metal a hardened adherent composition. It has also been foundthat M with the use of zircon sand as a mold for casting a block theblock can be gated into the bottom with cores that are placed about twoinches above the gate in a horizontal position having a head of teninches or more of metal above them. It has been found that the cores canbe readily removed from such a block even though the steel is curedexcessively hot. This would not e feasible with silica sand molds.

When desired, the zircon cores and molds may be washed with finesuspension'of silica to give extraordinarily smooth surfaces whileretainin the advantages above mentioned. In most mstancesfihowever, itis not necessary to use such a was with the zircon sand cores or molds.

I claim: a

1. A mold for castings in which the metal contacting surfaces are formedsubstantially of zircon and a binder.

2. A mold for castings in which the metal contacting surfaces are formedsubstantially of smooth grains of zircon.

LE RUE P. BENSING.

